Ah, you make it sound so easy :p
The best adding more healing classes can do is encourage people who like healing to play another healing job after they're done with their current, increasing the longevity of the healer pool. There really isn't diddly game mechanics can do to increase the healer pool size, because the desire to heal just isn't there in most people.
This is the kind of thing that's resolved by sweeping and drastic modifications to the fundamentals, it's not something a class bandaid can fix.
I COMPLETELY disagree. Mechanics can make a great deal of difference in the population of an archetype.
Think of healing as a Whm vs. Healing as a Dnc. They're completely different, and for the most part the overlap isn't any larger than it would be for, say, a Whm and a Blm.
I'm going to make a WoW example here, because it works better:
In WoW, there are 4 healing jobs--Priest, Druid, Shaman and Paladin. They ALL play very differently. Priests have two different specs that let them specialize, in a nutshell, in either tank or AoE healing. They play very differently. Druids specialize in HoT (Heals over Time) spells, which means they are best at preemptive healing. Shaman are pretty decent at both, but they are unique in that one of their heals "bounces" from target to target, and gets less effective with each one. So they can't predict who is going to get which subsequent heal, which makes the way they manage casts and select targets different. Paladins are pretty much devoid of AoE heals, and focus a lot on high critical rates for single-target heals.
Sure, all of them require someone to want to heal, but the variation there increases the chance that they ACTUALLY WILL. If you only have one healing job, anyone who wants to heal but doesn't enjoy the play style will do something else. That's losing the population when you don't need to. Plus, having different choices may drive someone who is uncertain if they'd like healing to go ahead and do it. I never found Priests that interesting (well, I didn't think I'd mind healing, but I really hated leveling the Priest when I tried it). But, I've entertained the idea of leveling a Druid or Shaman for a long time with the intention of trying to heal first and foremost, because their play style sounds interesting to me.
Same thing with Tanking. WoW has 4 classes that all function differently. I really enjoy Death Knight tanking, think I'd like Paladin tanking, don't know about Warriors and know I don't like Druid tanking. The play style makes a big difference.
If you want to argue it doesn't, then feel free to explain why XI had 17 DD jobs. CLEARLY someone that wanted to DD would be fine with just a Mnk, right?
Basically what Kachi said in a more FF-relevant manner in way fewer words.
One more example (this time FF specific).
Playing the support role, you had 3 options-- Rdm, Bard and Smn (despite that it wasn't often used). I know plenty of people that loved Rdm and hated Brd, or vice versa. They both wanted to play support, but had they been unable to play the one they wanted, they would have done something different rather than go the other (or Smn, since it was such a definition-less job). Edited, Mar 16th 2010 4:53pm by idiggory